Electrovalve unit, for loading washing liquid in a washing machine, having a device for controlling the temperature of said washing liquid

ABSTRACT

An electrovalve unit for filling a washing machine with a washing liquid has a first inlet for a washing liquid coming from a water supply, and a second inlet for heated liquid, at least one outlet for the liquid coming from the first and second inlet, apparatus for directing the washing liquid towards the outlet, and a device for measuring the temperature of the washing liquid passing through the outlet.

The present invention refers to an electrovalve unit (1) for loading washing liquid in a washing machine, said electrovalve unit having a device for controlling the temperature of said washing liquid.

It is known that washers, such as washing machines, dishwashers or similar, comprise at least an electrovalve connected to a water main to feed water for washing clothing and dishes.

Multiple-way electrovalves with several inlets are also known, each one controlled by a coil, and having a single outlet; at least one inlet is connected to the water main for the supply of cold water, and a second inlet is connected to a hot water source for the supply of preheated water to the washing machine.

Such electrovalves can work independently, so as to supply the washing machine either with cold water coming from the water supply or with hot water coming from the heat source, or mixing together the two so as to supply the washing machine with water at a pre-set temperature.

These last electrovalves provide a device to detect the water temperature; they are located on the water outlet duct of the electrovalve; such detecting device activates or deactivates the coil of one of the two water inlets, cold or hot, in function of the temperature detected in respect to the one set for the washing.

This device, generally a thermistor connected to a electronic control unit, is arranged externally to the electrovalve body without welding or over-moulding and it is dipped and mechanically bonded by a suitable material, normally by means of pouring epoxy resin, which requires a long time to dry and it does not have the best characteristics for heat transmission. This implies therefore very long, expensive and not very reliable operation cycles.

Moreover such an embodiment does not permit in case of failure of the thermistor detecting the temperature, to be replaced and therefore it is necessary to substitute the complete electrovalve with considerable costs for the user.

Another drawback is given by the fact that it is not possible to have a standard type electrovalve body as for the models using the temperature detecting device, the body must be carried out such in a manner to house such device.

In other known embodiments the coating of the thermistor detecting the temperature is obtained by injection over-moulding where, however, high pressures and temperatures are reached which are capable of jeopardizing in time the operation or the reliability of the said thermistor. Finally in the case of ultrasonic welding the thermistor bulb could break due to the vibrations stressing its mechanical strength.

The present invention has the aim of solving the above drawbacks related to the electrovalves equipped with a known type of sensor for temperature detection.

Within this frame, a first aim of the present invention is to indicate an electrovalve unit for loading washing liquid in a washing machine having a device for controlling the temperature of said washing liquid, of simple and compact construction, and thus economical, and which permits, in respect to the other known solutions, the achievement of higher precision in detecting the temperature, higher reliability in operation and simpler and more economical implementation.

A further aim of the present invention is to indicate an electrovalve unit of the above mentioned type with a higher reliability and simple to be repaired, with the aid of suitable means adapted to substitute only the temperature detection means.

These and further aims are achieved according to the present invention by an electrovalve unit for loading washing liquid in a washing machine having a device for controlling the temperature of said washing liquid, incorporating the features of the annexed claims, which form an integral part of the description herein.

Further aims, features and advantages of the present invention will become apparent from the detailed description which follows and the annexed drawings, which are supplied by way of an explanatory and non limiting example, wherein:

FIG. 1 shows a schematic top view of an electrovalve unit for loading a washing liquid using a temperature control device for the washing liquid, carried out according to the teachings of the present invention;

FIG. 2 shows a schematic side view of an electrovalve unit for loading a washing liquid in a washing machine according to the teachings of the present invention;

FIG. 3 shows a front part partially sectioned view of the electrovalve unit of FIG. 1;

FIG. 4 shows a schematic partial section of the electrovalve unit of FIG. 2;

FIG. 5 shows a schematic side view of a water temperature detecting device, according to the present invention;

FIG. 6 shows a schematic top view of the water temperature detecting device of FIG. 5.

FIGS. 1-3 show a top view, a side view and a front part partially sectioned view respectively of an electrovalve unit for loading washing fluid in a washing machine having a device for controlling the temperature of said washing liquid, carried out according to the teachings of the present invention.

In these drawings, reference 1 indicates a complete electrovalve unit, reference 2 indicates an inlet duct to connect the electrovalve unit to the water main, reference 3 indicates a second inlet connection to connect the electrovalve unit to a hot water supply.

Reference 4 indicates an outlet duct for the water coming from both the water main and the hot water supply; the three ducts number 2, 3 and 4 are hydraulically connected to one another.

The electrovalve unit 1, consisting in two electrovalves in the case depicted, is constructed and operates in a manner which is well known, and for this reason it will not be herewith described in details. It is however useful to remember that each electrovalve, referred as 5 and 6 respectively, each comprise a coil 7 suitable to drive some means of interception of the liquid coming from the water main through duct 2 or from the heat source through duct 3.

Reference 8 shows a temperature detecting device of the water flowing through duct 4 coming from duct 2 and/or 3.

The temperature detecting device 8, shown in FIGS. 5 and 6, has a body of plastic material 9 suitable for electric connections and which is not subject to remarkable heat deformation, said body consisting of a lower part 9A which is substantially of a parallelepiped shape and open at the lower side, and an upper base 9B which is larger than the section of the lower side 9A, the latter being adapted to close the lower part 9A.

The upper base 9B shows 2 side and perpendicular appendixes 10, each one having a latching tool 11 at the extremity.

Reference 12 shows a thermistor, for example a bulb type, with a sensitive element of the PCT or NTC type, each end thereof being welded to an end of the two electric terminals 13 and 14.

The other end of the terminals 13 and 14, getting through in the upper base 9B and protruding in the lower part 9A, are suitable for connections with terminals “FASTON” of the known type, to be connected to a electronic control unit. The terminals 13 and 14 are secured in the upper base 9B by means of mechanical non-return latches of the known type, so as to avoid them pulling out of the body 9 during subsequent assemblies.

The temperature detecting device 8 is mounted on the duct 4 by means of appendixes 10, the teeth 11 thereof latch on teeth 15 of opposite shape present on duct 4 (see FIG. 3). The teeth 11 of the appendixes 10 and the teeth 15 of the duct 4 are carried out with a radius free profile, such as to guarantee that after the snap in of the temperature detecting device 8 on duct 4, the device 8 cannot be pulled off except through a considerable axial force, over 100N prescribed by the Standards. The material constituting the body 9 of the temperature detecting device 8 is such so to guarantee the mechanical strength of the latching teeth 11; in an explanatory and non limiting embodiment, said material can be polyamide 66 with fiber glass.

The duct 4 in correspondence with the teeth 15 shows a flat surface 16 so as to allow a good support for the thermistor 12 on the external surface of the duct 4. Furthermore, alongside the flat surface 16 some shoulders 17 are provided suitable to prevent the device 8 pulling off sideways from the duct 4.

The thickness of the wall of duct 4 close to the flat surface in correspondence to the thermistor 12 can be reduced as regards to the thickness of the duct, to make easier the detection of the water temperature through the measuring device 8, for example, as shown in FIG. 4.

The material of the duct 4, in correspondence to the flat surface and in contact with the thermistor 12, can be constituted of another material as regards to the one for duct 4, that is with a more heat conductive material with respect to the one for the duct 4, to further improve the measurement of the temperature of the liquid inside the duct with the aid of the device 8.

To further improve heat transmission between the duct 4 and the temperature detecting device 8, a small quantity of heat conductive paste (approx 0.2 grams) is applied on the thermistor 12; for example, the conductive paste could be of the type of non silicone oil capable of sticking to the surface of the duct 4 and to the thermistor 12, without ever evaporating, thus guaranteeing a constancy of the heat conductivity coefficient within a wide range of temperature. For the maintenance, substitution or elimination of the temperature detecting device 8 from duct 4, it is sufficient to unlatch one of the two latching teeth and pull off the device 8 from duct 4.

In this way, it is possible to substitute or maintain the temperature detecting device 8 without damage or substitution of the electrovalve unit 1, with effective costs and time savings when being repaired.

This solution is so flexible such as to permit the use of the same electrovalve unit on those appliances which do not require measurement of the water temperature at the outlet duct of the valve itself; that is the electrovalve unit 1 can be used both with or without a temperature detecting device, obtaining in this manner a standardization of the electrovalves manufacture Furthermore, the transformation from one type to the other one does not require new tests of the electrovalve unit, nor new tests of the temperature detecting device, for the reason that the use of both the first and the second one does not affect the implementation and the assembly of the temperature detecting device 8 on the electrovalve unit 1.

The electrovalves of the electrovalve unit 1 can be of any type, for example of a ON/OFF type for a time loading of the washing liquid; or it can be of a differentiated loading type, that is with variable closing and/or opening of the water passage, as for the purposes of the present invention the use of one or the other type of electrovalve does not affect the manufacture and the assembly of the temperature detecting device temperature detecting device 8 on the electrovalve unit 1.

The manufacture of the temperature detecting device 8 is as follows:

moulding of body 9 of the device 8,

welding of the thermistor 12 to the terminals 13 and 14,

mounting the terminals 13 and 14 with the thermistor 12 welded inside the body 9 through slots present on the upper base 9B; the terminals are firmly secured in their work position by non return mechanical latches of a known type,

application of the conductive paste on the thermistor 12.

At this point the device 8 can be latched on duct 4 of the electrovalve unit 1 by means of the teeth 11 located on the device 8 with teeth 15 present on the duct 4.

The operation of the temperature detecting device 8 is very simple; i.e. it detects the temperature of the liquid passing through the duct 4 and transmit the measured data to a electronic control unit, the latter being not represented nor described as the type is known, and in function of the temperature detected by the device 8 in respect to the one selected by the user, the electronic control unit will activate or disactivate the passage of the cold or hot water in order to reach the desired temperature, by controlling the opening or closing of one of the electrovalves.

From the above description, the features of the present invention are apparent.

In particular the description concerns an electrovalve unit for loading a washing liquid in a washing machine having a device for controlling the temperature of the washing liquid from the outlet duct of said electrovalve unit, mounted, such that it can be removed on a duct of the said electrovalve unit.

According to the invention, means of snap in latches of said temperature detecting device on the outlet duct of the washing liquid from the said electrovalve unit are provided.

The temperature detecting device is carried out such in a way to not suffer any considerable stress during its assembly on the electrovalve unit.

From the above description it is clearly indicated the advantages of the present invention; the following in particular, are to be underlined:

simple manufacture of the electrovalve unit, in view of the fact that it is sufficient to obtain a seat and some latching teeth on the outside of the outlet duct;

simple manufacture of the temperature detecting device, as it is not necessary to have high pressure and/or temperatures to assemble it on the electrovalve unit;

simple maintenance or substitution of the temperature detecting device, as it is possible to assemble and/or removal from the electrovalve unit without damaging the one or the other, as the device is latched on only mechanically to the electrovalve unit by means of latching teeth;

greater functionality and reliability over time of the temperature detecting device, as the thermistor is not subject to violent and stressing operations;

the electrovalve unit can be used with or without the temperature detecting device thus achieving a standard production of the electrovalve unit itself.

The description of the present invention refers to an electrovalve unit for washing machines whereon outlet duct of the said valve a temperature detecting device is latched; this does not prevent the type and the manner of assembling the temperature detecting device from being applied to any duct, of any application, where flowing a liquid thereof the temperature is required to be detected.

It is clear that many changes are possible for the man skilled in the art on an electrovalve unit for loading a washing liquid in a washing machine which has a temperature detecting device of the washing liquid on the outlet duct of the said electrovalve unit, described as an example, without departing from the novelty spirit of the inventive idea. 

1. Electrovalve unit for loading a washing liquid in a washing machine comprising a first inlet for a washing liquid coming from a water main, and a second inlet for heated liquid, at least one outlet for the liquid coming from said first and second inlet, means for driving and intercepting the passage of said washing liquid towards said outlet, a temperature detecting device for the washing liquid passing through said outlet wherein said temperature detecting device is removably assembled from said outlet of the said electrovalve unit.
 2. Electrovalve unit, according to claim 1, wherein said outlet comprises first latching means for said temperature detecting device.
 3. Electrovalve unit, according to claim 1, wherein said temperature detecting device comprises a body of plastic material, which comprises second latching means for said device to the said outlet, the latter means being complementary to said first latching means.
 4. Electrovalve unit, according to claim 3, wherein said second latching means are of a snap in type.
 5. Electrovalve unit, according to claim 1, wherein said temperature detecting device further comprises a sensor, said sensor being connected to terminals for said sensor to be connected to an electronic control unit being part of the machine.
 6. Electrovalve unit, according to claim 5, wherein said sensor is a thermistor, of a type comprising a bulb with sensitive element of the PTC and/or NTC type.
 7. Electrovalve unit, according to claim 1, wherein said outlet comprises a flat surface capable of assuring a good contact between said outlet and said thermistor.
 8. Electrovalve unit, according to claim 7, wherein said outlet in correspondence with said flat surface is thinner to make it easier when detecting the temperature of the liquid by the thermistor.
 9. Electrovalve unit, according to claim 7, wherein said outlet in correspondence to said flat surface is carried out with a more heat conductive material than that used for the remaining part of said outlet.
 10. Electrovalve unit, according to claim 7, comprising, alongside said flat surface, latching means for preventing said temperature detecting device from pulling off sideways of the outlet.
 11. Electrovalve unit, according to claim 7, comprising additional means to increase heat conductivity between said outlet and said thermistor.
 12. Electrovalve unit, according to claim 11, wherein said means capable of increasing heat conductivity comprise a heat conductive paste of a non silicon oil type.
 13. Method for manufacturing an electrovalve unit comprising a temperature detecting device to measure the temperature of a liquid passing through an outlet of said electrovalve unit, wherein the manufacture of said electrovalve unit and of said temperature detecting device are obtained through operations independent from each other.
 14. Method, according to claim 13, wherein coupling of said temperature detecting device with said electrovalve unit is obtained subsequently to their manufacture.
 15. Method of coupling a temperature detecting device with an electrovalve unit in a snap in way.
 16. Washing machine comprising an electrovalve according to claim 1, and a duct through which said washing liquid passes for being sensed by said temperature detecting device. 